A 10-YEAR-OLD boy who had normal developmental milestones except for a speech delay was referred for evaluation of an asymptomatic heart murmur. His parents, who are first cousins, have 2 other healthy children.

On physical examination, the child was well nourished and without dysmorphic features. The cardiac examination revealed a grade 2/6 systolic murmur at the left lower sternal border. His peripheral pulses were equal, and the blood pressure in all 4 extremities showed no abnormalities. Findings of the remainder of the examination were unremarkable.

A chest radiograph; echocardiogram; and serum calcium, magnesium, and electrolyte measures showed no abnormalities. A representative electrocardiogram is shown in Figure 1. An audiogram demonstrated severe sensorineural deafness in both ears.